A process for forming a wiring layer in a semiconductor device uses a so-called damascene process including forming a groove pattern and hole pattern in an interlayer insulating film and then filling groove and holes with a wiring material. The damascene process is classified into a single damascene process in which via hole filling and wiring trench filling are performed separately, and a dual damascene process in which via hole filling and wiring trench filling are performed simultaneously.
Recently, low-dielectric films (low-k films) have been used as interlayer insulating films in which a wiring layer is buried to increase the speeds of semiconductor devices.